High Levels of Black Carbon Found in Chicago Air

When the Chicago City Council recently passed an ordinance to reduce emissions from construction equipment working on city jobs, it touched on a larger problem: harmful amounts of diesel exhaust in the city. Journalist Kari Lydersen tested the air and found troubling emission levels in some neighborhoods.


When the City Council last week passed an ordinance to reduce emissions from construction equipment working on city jobs, it touched on a larger problem: harmful amounts of diesel exhaust in Chicago’s air.

Residents of several Chicago neighborhoods are likely exposed to diesel emissions at levels many times higher than the average for urban areas, testing by the Chicago News Cooperative shows. In nearly 100 hours of spot testing in early April–near dense residential areas, schools and parks in both working-class and wealthier neighborhoods–the CNC found elevated levels of black carbon. Testing for black carbon is a common way to determine levels of diesel exhaust, which is linked to higher risks of cancer, heart disease and lung disease and is also known to exacerbate allergies and asthma.

(See sidebar to learn how the testing was done.)

Though the testing does not meet the rigorous standard of peer-reviewed scientific literature, it does indicate that, even years after the decline of heavy industry in Chicago, air quality in many city neighborhoods remains a concern. Experts said the tests indicate troubling levels of diesel pollution in Little Village, Lincoln Park, Ukrainian Village, Wicker Park, Pilsen and other areas.

“Some of the results may be of concern for potential health effects in exposed individuals, particularly in sensitive subpopulations such as children and elderly,” said Serap Erdal, an associate professor of occupational and environmental health sciences at the University of Illinois at Chicago School of Public Health.

Black carbon, a component of particulate emissions from diesel exhaust, is itself harmful and is usually combined with other toxic compounds in diesel exhaust. Diesel emissions also contain a relatively high proportion of very fine particles, scientists say, which are particularly damaging because they can penetrate deeply into the lungs and even into the bloodstream.

“There’s suspicion that diesel is a lot more toxic than other types of particulate matter because of the things it’s enriched with,” said Scott Fruin, an assistant research professor of environmental health at the University of Southern California, Keck School of Medicine.

For example, diesel exhaust carries metals as well as hydrocarbons believed to cause cancer. Diesel emissions also contain oxides of nitrogen, which form smog and contribute to respiratory problems, and toxic compounds including benzene and dioxin.

Diesel engines produce more harmful exhaust than standard gasoline engines partly because of the different combustion processes, meaning diesel exhaust is laced with more particles of incompletely-burned fuel.

Bruce Hill, senior scientist for the Clean Air Task Force, an advocacy group, said black carbon particles are “like little sponges that pick up other bad stuff, things from wear and tear in the engine, lubrication fluids, metals, toxics.”

The Clean Air Task Force estimates that in the Chicago metropolitan area, particulates from diesel emissions cause about 723 premature deaths, 1,100 heart attacks, 500 cases of chronic bronchitis and 28,200 asthma attacks each year.

Cheryl Newton, director of the federal Environmental Protection Agency’s Region 5 Air and Radiation Division, said the Chicago area as a whole meets federal standards for particulate matter.

Major U.S. cities generally have background levels of 1 to 3 micrograms of black carbon per cubic meter. There are no federal standards specifically for diesel emissions, but California, which has taken a strict approach to diesel pollution, has an eight-hour health standard for diesel particulate that converts to 2 to 3 micrograms per cubic meter of black carbon.

Spot testing around Chicago showed background levels of between 1 and 2 micrograms of black carbon per cubic meter. And near trucking routes and rail yards in several locations, the levels were significantly higher.

Pilsen’s Benito Juarez High School sits at the corner of two major trucking routes: Ashland Ave. and Cermak Ave. On a Wednesday afternoon in early April at the bus stop near the school’s entrance, average black carbon levels were 7.2 micrograms per cubic meter.

The next day, a state Bureau of Bridges machine was pounding a metal spike into a sidewalk in Pilsen as children left Pilsen Academy half a block away. Black carbon levels measured across the street from the machine for half an hour averaged 24 micrograms per cubic meter, with two peak readings over 800.

The average black carbon level was 4.8 micrograms per cubic meter in Ukrainian Village near the intersection of Western Ave. and Grand Ave., just east of Smith Park. In Little Village, in front of homes on 31st Street west of Kedzie Ave., the level on a late weekday morning was 20.5 micrograms.

The low-income, picturesque enclave of Marktown is situated between a BP oil refinery, and steel mills and other heavy industry in northwest Indiana. While these sources do not emit much black carbon, residents are exposed to diesel emissions from trucks that serve the facilities. On a breezy early morning, average levels on a residential Marktown street were 4.5 micrograms per cubic meter.

Upscale areas were no better off. Testing in Lincoln Park showed an average 23 micrograms between Webster Place and Janssen Ave., a residential street. An overall average of 6.7 micrograms per cubic meter was found in three separate residential and commercial strips in trendy Wicker Park.

The City Council ordinance passed last week aims to reduce diesel emissions from construction equipment used on city jobs by requiring contractors to use cleaner fuel and better pollution-control technology.

Public health experts said the new Chicago law is an important step in improving the city’s air quality. But city officials have little power to regulate the trucks and locomotives that account for the majority of the city’s diesel emissions.

“When you have a smokestack, it’s high, it’s designed to disperse things over a wide area,” said Brian Urbaszewski, environmental health programs director for the Respiratory Health Association of Metropolitan Chicago. “But with diesel tailpipes it comes out right at street level and stays concentrated in the immediate area, affecting people living, working and going to school in those areas.”

Scientists say that while construction vehicles contribute significantly to overall diesel emissions in a city, their effect is usually temporary.

“People who are vulnerable and sensitive – asthmatics, the elderly — might have a concern in the short-term” because of construction equipment on a worksite, said Fruin. “But no one’s exposed to the equipment for very long.”

Disease risk typically is linked to long-term exposure, so rail yards and truck routes likely pose more serious problems.The E.P.A. mandates certain pollution control equipment for all new diesel engines. But advocates point out that dirty diesel engines remain in service for many decades. Older locomotives are typically used as switchers in rail yards, which means they can have a disproportionate impact on nearby residents.

Emissions from locomotive engines can be worse than those from truck engines. Erdal said her own work and other research, including a 2007 study of a northern California rail yard, indicate that the particulate matter from locomotives is typically smaller and has higher concentrations of some carcinogens.

In the residential neighborhood next to BNSF’s massive Corwith rail yard in Brighton Park, levels averaged 2.4 micrograms per cubic meter on two separate days. While the readings were within the normal range, they were taken during high winds, which Fruin said would disperse pollutants and potentially understate the average levels.

Amy McBeth, a BNSF spokeswoman, said the company has taken steps to reduce diesel emissions in its Chicago-area rail yards by using low-sulfur fuel, installing automatic gates that cut truck idling time in half, and other measures.

In Pilsen, an elevated rail yard connected to the 16th Street viaduct stands directly above the dense working-class, immigrant neighborhood. Average levels were 10.2 micrograms per cubic meter one night as yellow locomotives emitted hissing plumes of bluish exhaust.

Unlike other air pollutants that disperse across large regions, the health effects of diesel emissions are primarily local and fluctuate widely, depending on the amount of truck or train traffic and the weather. Three quarters of a mile upwind from the Pilsen rail yard with the 10.2 microgram average, the average was 2 micrograms per cubic meter.

Erdal and Urbaszewski said industry and government officials should be especially concerned about diesel emissions in Pilsen, Little Village and surrounding Southwest Side neighborhoods, considering the presence of the city’s two archaic coal-fired power plants and other nearby sources of air pollution.

While these sources don’t emit black carbon, their pollutants combine with diesel emissions to increase the harmful effects on the largely low-income, Latino residents.

“All the diesel exhaust is on top of the coal plant that’s already causing widespread air pollution in the urban area,” Urbaszewski said. “People are getting a one-two punch.”